1. Field of the Invention
The present invention relates to a single facer suitable for consecutive manufacture of a single faced corrugated fiberboard.
2. Description of the Related Art
FIG. 12 is a side elevational and cross-sectional view illustratively showing a structure of a prior single facer, and FIG. 13 is an enlarged view showing a principal portion of FIG. 12. As shown in FIG. 12, a single facer 200, which consecutively manufactures a single faced corrugated fiberboard, comprises, in addition to an upper corrugating roll 1 having a corrugated surface (flutes) on its outer circumferential surface, a lower corrugating roll 2 and a pressure roll 3 in the form of a basic roll arrangement.
In this roll arrangement, the lower corrugating roll 2 is disposed at a position where a corrugating medium 4 can be interposed between the same lower corrugating roll 2 and the upper corrugating roll 1, with the lower corrugating roll 2 having, on its outer circumferential surface, flutes engaging with the upper corrugating roll 1. The pressure roll 3 is located on the downstream side of the upper corrugating roll 1 to come into contact with the flute tip portions of the outer circumference of the lower corrugating roll 2 under the action of an appropriate nip pressure.
In addition, in the lower corrugating roll 2 and at positions close to its outer circumferential surface, a plurality of transverse holes 10 are bored at an equal pitch interval on a concentric circle in parallel to the central axis of the lower corrugating roll 2. An end portion of each of these transverse holes 10 is placed into contact with a side end surface of the lower corrugating roll 2 and is made to communicate with a non-shown air suction unit (air suction source) through a sliding surface with the lower corrugating roll 2 and a piping system being in communication with some of the transverse holes 10. Further, in the circumferential surface of the lower corrugating roll 2, a plurality of circumferential slit grooves 11 are formed along the axial direction of the lower corrugating roll 2 at an adequate interval. The transverse holes 10, the circumferential slit grooves 11, the air suction unit and the piping system constitute an air suction mechanism.
That is, with this air suction mechanism, on operating the non-shown air suction unit, an air suction from the circumferential slit grooves 11 made in the circumferential surface of the lower corrugating roll 2 takes place through the piping system and the respective transverse holes 11.
The upper corrugating roll 1 and the lower corrugating roll 2 are for the purpose of shaping (corrugating) a corrugating medium 4 into a corrugated medium 6 while the corrugating medium 4 passes through an engaging section defined therebetween. At this time, a suction force generated due to the non-shown air suction unit causes the suction of the corrugated medium 6 through the transverse holes 10 and the circumferential slit grooves 11 to make it come closely into contact with the flute-made surface of the lower corrugating roll 2, with the lower corrugating roll 2 transferring the corrugated medium 6 up to a joining section between the lower corrugating roll 2 and the pressure roll 3 in a state of holding it in the closely contacting condition.
Furthermore, a gluing roll 7 is disposed on the downstream side of the location of the upper corrugating roll 1 but on the upstream side of the location of the pressure roll 3 on the circumferential surface of the lower corrugating roll 2, thereby applying a glue onto the flute tip portions of the corrugated medium 6. This gluing roll 7 rotates while coming into with a roll 7a rotating in a dipped condition into a glue 8 so that its entire circumferential surface always undergoes the even application of the glue 8, and rotates while coming into contact with the flute tip portions of the corrugated medium 6, thereby applying the glue 8 onto the flute tip portions of the corrugated medium 6.
On the other hand, on the downstream side of the location of the gluing roll 7 on the circumferential surface of the lower corrugating roll 2, the pressure roll 3 equipped with a non-shown heating unit is placed to come into contact with the lower corrugating roll 2. Further, this pressure roll 3 guides a linerboard 5 into a gap defined with respect to the lower corrugating roll 2, and further bonds (adheres) the linerboard 5 to the glue 8 applied corrugated medium 6 under pressure in the gap with the lower corrugating roll 2 in a state of heating by the non-shown heating unit, thus producing a single faced corrugated fiberboard sheet 9.
With this construction, the corrugating medium 4 is first guided by the upper corrugating roll 1 into a gap between the upper corrugating roll 1 and the lower corrugating roll 2 to be flute-shaped (corrugated) while passing through the engaging section between the upper corrugating roll 1 and the lower corrugating roll 2, thus producing the corrugated medium 6.
Subsequently, the corrugated medium 6 produced through the engaging section between the upper corrugating roll 1 and the lower corrugating roll 2 is drawn by the air suction mechanism, and delivered in accordance with the rotation of the lower corrugating roll 2 in a state of being brought closely into contact with the flute-made surface of the lower corrugating roll 2.
When the corrugated medium 6, being delivered by the lower corrugating roll 2, reaches the gap between the gluing roll 7 and the lower corrugating roll 2, the glue 8 is applied through the gluing roll 7 onto its flute tip portions, and then conveyed into the gap between the pressure roll 3 and the lower corrugating roll 2.
In the gap between the pressure roll 3 and the lower corrugating roll 2, the corrugated medium 6 holding the applied glue 8 on its flute tip portions and the linerboard 5 guided by the pressure roll 3 from a different direction are joined (adhered) to each other under pressure while being heated by the non-shown heating unit, thus creating the single faced corrugated fiberboard sheet 9. The created single faced corrugated fiberboard sheet 9 is shifted into the next process.
In the case of the prior single facer 200 thus constructed, as shown in FIG. 13, when the corrugating medium 4 is flute-shaped by the flutes formed on the upper corrugating roll 1 and the lower corrugating roll 2 in the engaging section between both the corrugating rolls 1, 2, the flutes of the both the corrugating rolls 1, 2 are strongly brought into pressing contact with each other in a state where the corrugating medium 4 is caught in therebetween, so that a nip pressure being as large as several tens kgf/cm.sup.2 works between the flutes of both the corrugating rolls 1, 2 and slip occurs between the flutes through the corrugating medium 4 with the rotation of both the corrugating rolls 1, 2, which causes a strong frictional force to work on the tooth surfaces of the flutes being in gear with each other.
In addition, friction also occurs between the corrugating medium 4 and the tooth strings of both the corrugating rolls 1, 2 immediately before the engagement because of the sliding contact therebetween, which causes the flutes to be worn. Accordingly, even if the corrugating medium 4 with an ordinary quality is put to use, when being used for 0.5 to 1 year, each of the rolls working for the corrugation is required to be replaced with new one, or the flutes thereof are necessary to re-shave.
The friction phenomenon the flutes of the corrugating rolls 1, 2 experience depends greatly upon the quality of the corrugating medium, and particularly, in the case of use of a low-quality corrugating medium containing a large amount of hard impurities such as an ash content, the abrasion of the flutes of the corrugating rolls 1, 2 more takes place, which further shortens their service life. In an extreme case, there is the possibility that they can not be used if being put into operation for 2 to 3 months.
Moreover, the corrugating rolls 1, 2 are expensive, and the limit of the revival by the re-shaving is approximately three times and they are scraped afterwards, and hence, the business circles have intense aspirations toward a technical solution for effectively extending the service lives of the corrugating rolls 1, 2.
Besides, a detailed description will be made of the wearing phenomenon the flutes of the aforesaid corrugating rolls 1, 2 experience. The flutes of the upper corrugating roll 1 are further subject to the sliding friction with respect to the corrugating medium 4 or the corrugated medium 6 as compared with the lower corrugating roll 2 where the corrugated medium 6 is absorbed on its flute-made surface by the air suction mechanism, so that the abrasion of the flutes of the upper corrugating roll 1 is more considerable as compared to the flutes of the lower corrugating roll 2.
On the other hand, for solving the above-mentioned problems, there has been known a single facer in which, in place of the upper corrugating roll of the above-described prior single facer 200, an air pressurization corrugating mechanism is provided which accomplishes the corrugation by pressing a corrugating medium against flutes shaped on a circumferential surface of a lower corrugating roll through the use of an air pressure. That is, in this single facer, the upper corrugating roll 1 is omitted from the above-mentioned single facer 200 and only one roll equivalent to the lower corrugating roll 2 is used as the corrugating roll.
Referring to drawings, a description will be given of a single facer equipped with such a prior air pressurization corrugating mechanism. FIG. 14 is a side elevational and cross-sectional view illustratively showing the single facer, and FIG. 15 is an enlarged, side-elevational and cross-sectional view showing a principal section (where an air pressurization corrugating mechanism 12 is brought close to a lower corrugating roll 2) thereof.
As shown in FIG. 14, a prior single facer 210 with an air pressurization corrugating mechanism has substantially same construction as that of the above-mentioned FIG. 12 prior single facer 200 except that the upper corrugating roll 1 is removed and an air pressurization corrugating mechanism 12 is provided instead. In the illustrations, the same numerals as those in the above description signify the same or corresponding parts, and therefore, the detailed description thereof will be omitted for brevity.
The air pressurization corrugating mechanism 12 is, as shown in FIG. 15, composed of a nozzle body 13 for introducing high-pressure air 16, a sealing plate 14 placed at a lower corrugating roll 2 side end portion of the nozzle body 13 to extend along a circumferential surface of a lower corrugating roll 2, and a sealing member 15 mounted on a surface of the sealing plate 14 which is in an opposed relation to the lower corrugating roll 2 circumferential surface. The sealing member 15 has a circumferential dimension to cover at least two of the flutes made on the circumferential surface of the lower corrugating roll 2.
In the nozzle body 13, a transverse cross section of its air injection opening 13a assumes an elongated quadrangle forming a slit configuration, and in its inner-size transverse cross section, its long side approximately has the same length as that of the axial length of the lower corrugating roll 2, while its short side is substantially above the flute pitch of the lower corrugating roll 2.
In addition, as shown in FIGS. 14 and 15, the air pressurization corrugating mechanism 12 is situated on the upstream side of a gluing roll 7 along the outer circumference of the lower corrugating roll 2 to define a gap corresponding to the thickness dimension of a corrugating medium 4 with respect to the flute tip portions of the lower corrugating roll 2, and when the corrugating medium 4 is interposed between the sealing member 15 of the air pressurization corrugating mechanism 12 and the flute tip portions of the lower corrugating roll 2, the air leakage from the space between the nozzle body 13 and the front side (one side of the corrugating medium 4 which does not face the lower corrugating roll 2) surface of the corrugating medium 4 is relatively little, so that an airtight condition is substantially maintainable.
That is, in a manner that high-pressure air 16 is supplied from a non-shown air supply unit to the interior of the nozzle body 13, the space between the nozzle body 13 and the front side surface of the corrugating medium 4 is maintainable in a high-pressure atmosphere, so that a high static pressure can work on the front side surface of the corrugating medium 4.
With this construction, when the corrugating medium 4 is fed into the gap between the air pressurization corrugating mechanism 12 and the lower corrugating roll 2, as shown in FIG. 15, in the gap between the sealing plate 14 and sealing member 15 of the air pressurization corrugating mechanism 12 and the flute tip portions of the lower corrugating roll 2, the high-pressure air 16 supplied through the nozzle body 13 presses the corrugating medium 4 against the flute-made surface of the lower corrugating roll 2 at a stretch, thereby shaping the corrugating medium 4 into a corrugated medium 6.
Furthermore, on the rear surface side of the corrugating medium 4 (corrugated medium 6), an air suction mechanism sucks air existing in the gap between the rear surface of the corrugating medium 4 (corrugated medium 6) and the circumferential surface of the lower corrugating roll 2 through circumferential slit grooves 11 and transverse holes 10, and therefore, the space between the rear surface of the corrugating medium 4 (corrugated medium 6) and the circumferential surface of the lower corrugating roll 2 always goes into a negative-pressure condition, which assists the corrugating process for the corrugating medium 4 by the compressed air 16 jetted from the air pressurization corrugating mechanism 12.
Still further, owing to the action of the air suction mechanism, the corrugated medium 6 produced is drawn to the flute-made surface of the lower corrugating roll 2 to reach a closely contacting condition, and the occurrence of the spring back which is a phenomenon of returning to the original configuration on the removal of the stress working on the corrugated medium 6 is suppressible, and further, the corrugated medium 6 is conveyed to between the lower corrugating roll 2 and the pressure roll 3 in a state of being maintained in the closely contacting condition against the centrifugal force of the lower corrugating roll 2.
Incidentally, as well as the single facer 200 including the aforesaid upper corrugating roll 1, in the process that the corrugated medium 6 is transferred by the lower corrugating roll 2 to between the lower corrugating roll 2 and the pressure roll 3, the gluing roll 7 applies a glue 8 onto its flute tip portions, and subsequently, in the gap between the pressure roll 3 and the lower corrugating roll 2, the corrugated medium 6 is joined (adhered) to a linerboard 5, guided by the pressure roll 3 from a different direction, under pressure while being heated by a non-shown heating unit, thereby forming a single faced corrugated fiberboard 9. Further, the formed single faced corrugated fiberboard 9 is shifted to the next process.
However, in the case of such a prior single facer 210, when the high-pressure air 16 is jetted from the front surface side of the corrugating medium 4 in the corrugation processing for the corrugating medium 4 so that the rear surface thereof reaches the inter-flute bottom surface of the lower corrugating roll 2, the air pressure producing that high-pressure air 16 needs to be as high as approximately 3 to 5 kg/cm.sup.2, and in this case, there are problems in that a strong compressed air supply unit becomes necessary and a large amount of air is necessary to consume.
In addition, at the corrugation processing for the corrugating medium 4 in the gap between the air pressurization corrugating mechanism 12 and the lower corrugating roll 2, a slight time is taken from when the corrugating medium 4 is subjected to the jetting of the high-pressure air 16 to start to deform until the rear surface thereof reaches the inter-flute bottom surface of the lower corrugating roll 2, and hence, before the corrugating medium 4 reaches the inter-flute bottom surface of the lower corrugating roll 2, the lower corrugating roll 2 rotates to enter the next flute forming process, with the result that, as shown in FIG. 16 (a side-elevational and cross-sectional view corresponding to FIG. 15), the height of the flutes of the corrugating medium 4 corrugated becomes lower than that of a single faced corrugated fiberboard sheet produced through the use of the single facer 200 shown in FIG. 12, which can deteriorate the shock absorbing ability of the corrugated fiberboard sheet finally produced. This tendency to decrease the flute height grows as the rotational speed of the lower corrugating roll 2 increases.
More specifically, FIG. 17A shows a flute configuration of the single faced corrugated fiberboard sheet 9 produced by the single facer 200 shown in FIG. 12 and FIG. 17B illustrates a flute configuration of the single faced corrugated fiberboard sheet 9 produced by the single facer 210 shown in FIG. 14, and as shown in FIGS. 17A and 17B, after the corrugation processing by the air pressurization corrugating mechanism 12, the flute configuration of the single faced corrugated fiberboard sheet 9 produced by the adhesion to the linerboard S is broken by the spring back, and its flute height H' becomes lower than the flute height H of the single faced corrugated fiberboard sheet 9 produced by the single facer 200, which can deteriorate the shock absorbing ability of the corrugated fiberboard sheet finally manufactured.